Well, you could do a fanfic where the Akatsuki members from Naruto are villains in the My Hero Academia setting. They could be after the quirks of the students. And maybe Deku somehow gets involved with Naruto and they figure out a way to stop the Akatsuki together. Or perhaps a story where All Might meets the Hokage. They could exchange ideas on leadership and heroism.
One idea could be Deadpool getting transported to the My Hero Academia universe and causing chaos with his fourth - wall - breaking antics while also teaming up with Deku to take on a powerful villain. Another could be Deadpool trying to join UA High and his interactions with the teachers and students during the entrance exam.
One idea could be that Naruto characters are transported to the My Hero Academia world. Naruto himself could be seen as having a very unique quirk, like his chakra manipulation could be considered a superpower. They could team up with the students of UA to fight against a common enemy, like a group of villains who are after the secrets of chakra. Another plot could involve the My Hero Academia characters traveling to the Naruto world and learning about ninjutsu and how it differs from their quirks.
One idea could be a crossover where Naruto characters end up in the My Hero Academia world. For example, Naruto could meet Midoriya and they could learn from each other's determination. Another could be a story where the quirks in My Hero Academia are similar to the ninja abilities in Naruto. Maybe a character has a quirk like shadow clones. A third idea might be a time - travel fanfiction where a My Hero Academia character goes back in time to the Naruto era and has to adapt to the different fighting styles and cultures there.
A possible plot is that Midoriya and Uraraka are sent to a parallel universe where they are not heroes, but ordinary people. They have to find a way to get back to their own world while also realizing how important their relationship is to them even without their hero identities. Another interesting plot could be that Uraraka starts to doubt her own abilities as a hero, and Midoriya is there to constantly encourage her and help her regain her confidence. This would bring them closer together. And then there could be a plot where they find an ancient artifact during a mission that has some sort of power related to love, and it affects their relationship in unexpected ways.
One idea could be that the Pokemon have quirks like in My Hero Academia. For example, a Pikachu with an electricity - based quirk that allows it to not only use electric attacks but also manipulate the electricity in unique ways, like creating shields. Another idea is to have the characters from My Hero Academia become Pokemon trainers. Deku could start his journey with a weak - looking Pokemon that he trains to become very powerful, just like he does with his quirk. And a third idea could be to set the Pokemon world in the My Hero Academia universe, where there are both heroes and villains trying to control powerful Pokemon for different purposes.
One idea could be to explore the backstory of a minor character. For example, what was the life of a random student in Class 1 - B like before coming to U.A. High? Another could be a 'what if' scenario, like what if Izuku Midoriya didn't get One For All. Maybe he'd develop his own unique quirk through sheer determination and hard work. Or a fanfic could focus on the villains' side, showing how they came to be and their motives in more depth.
One idea could be a crossover with the Harry Potter universe. Imagine Deku going to Hogwarts and learning magic while also using his Quirk. He could make friends with Harry and they could learn from each other's skills. Another idea is a crossover with the Avengers. The heroes from My Hero Academia could team up with the Avengers to fight a common, super - powerful enemy. Maybe All Might and Captain America could have an interesting conversation about leadership and heroism.
An interesting concept would be an OC who has a quirk that is based on art. For example, they can bring paintings to life. This OC could be a part of an art school within the My Hero Academia universe and use their quirk to fight villains who are attacking art galleries or museums. They would also have to train their quirk to be more combat - effective.
One interesting crossover could be the characters swapping their powers. For example, Deku having Naruto's chakra and being able to perform jutsus. It would be really cool to see how he would use them in the My Hero Academia world. Another could be the heroes and ninjas teaming up to fight a common enemy. Maybe the League of Villains and some of the Akatsuki members joining forces, and then the heroes and ninjas having to combine their skills to defeat them.
One idea could be that the OC's voice quirk is a secret weapon against a new type of villain who can't be defeated by normal quirks. The OC has to keep their quirk hidden until the right moment. Another plot could involve the OC's voice quirk being stolen by a villain, and they have to find a way to get it back. Maybe the OC uses their voice to communicate with animals in the My Hero Academia world, and this leads to an adventure where they have to stop a group of villains who are using animals for evil purposes.